1. Technology Field
The disclosure relates to a memory retry-read method, and particularly relates to a memory retry-read method of a rewritable non-volatile memory module, and a memory control circuit unit and a memory storage device using the method.
2. Description of Related Art
The growth of digital cameras, mobile phones, and MP3 players has been rapid in recent years. Consequently, the consumers' demand for storage media has increased tremendously. Owing to the characteristics of data non-volatility, lower power consumption, smaller size, non-mechanical structure, and fast read and write speeds, rewritable non-volatile memory is most suitable for portable electronic products, such as laptops. A solid-state drive is a memory storage device adopting flash memory module as the storage medium. For these reasons, flash memory has become a popular part of the electronic industries.
Generally speaking, a physical programming unit in a flash memory module is formed by a plurality of memory cells arranged on the same word line. When data are to be programmed to the physical programming unit, storage states of the memory cells are defined by modifying threshold voltages of the memory cells, thereby storing data. However, due to various factors, such as wearing of the memory cells due to an excessive number of times of erasing, long time storage, reading disturb, and the like, a threshold voltage distribution of the memory cells of the flash memory module may be deviated, making the storage states of the memory cells not correctly identifiable. Thus, when a predetermined threshold voltage is applied to the word line to read the data stored in the physical programming unit, the read data may include erroneous bits.
When the data read from the physical programming unit include erroneous bits, a memory control circuit unit of the flash memory module may try to correct the read data. If the read data are unable to be corrected, the memory control circuit unit may execute a retry-read operation on the physical programming unit where a read operation is executed. Generally speaking, the memory control circuit unit may adjust a predetermined read voltage based on a retry-read parameter provided by the manufacturer, so as to execute the retry-read operation on the physical programming unit and thus obtain new data. However, during execution of the retry-read operation, the memory control circuit unit is only allowed to choose the retry-read parameter based on a fixed sequence of priority. Under this circumstance, if an effective retry-read parameter is lower-ranked in the sequence, the memory control circuit unit needs to choose a certain number of retry-read parameters to execute the retry-read operations before choosing the effective retry-read parameter. Thus, a certain amount of time may be spent on executing the retry-read operation.
Nothing herein should be construed as an admission of knowledge in the prior art of any portion of the disclosure. Furthermore, citation or identification of any document in this application is not an admission that such document is available as prior art to the disclosure, or that any reference forms a part of the common general knowledge in the art.